1. Field of Invention
The present invention relates to a parallax barrier 3D image display method, and more particularly to a vertical strip parallax barrier design method to avoid transverse ghost images generated by a conventional parallax barrier and directed to arrangement of sub-pixels on a screen of a flat panel display, which displays multi-view 3D images with minimal ghost images, thereby achieving the purpose of optimum 3D image display.
2. Related Art
FIG. 1 is a schematic view of a conventional vertical strip parallax barrier. The basic optical structure of the vertical strip parallax barrier 10 is formed of vertical strip light-transmissive elements 11 (provided with a horizontal width B0 and a vertical height H) and vertical strip shielding elements 12 (provided with a horizontal width B0 and a vertical height H). The light-transmissive elements 11 and the shielding elements 12 are arranged alternately in a horizontal direction, so as to form a parallax barrier active region 15 having an area of W×H.
Directed to the vertical strip parallax barrier 10, FIG. 2 is a schematic view of a conventional multi-view 3D image (hereinafter, the 4-view is illustrated as an example). The 4-view 3D image 20 is usually displayed by a screen of a flat panel display (e.g., LCD, Plasma, or OLED display). The screen of the flat panel display is formed of (M+1)×(N+1) sub-pixel units 21, and a single sub-pixel unit 21 has a P×h image display area. Thus, the maximum image display area of the 4-view 3D image 20 is W′×H′, in which W′=P(M+1), H′=h(N+1). In practical design, generally W˜W′ and H˜H′.
Additionally, the 4-view 3D image 20 is formed by the arrangement of 4 view images Vj,i having equal parallax effect. Here, V indicates the number of a view and 0≦V≦3; i,j are positions of the sub-pixel units 21 and 0≦i≦M, 0≦j≦N. In the arrangement method, on any horizontal line (e.g., j=j′), the 4-view image arrangement Vj,i, is in unit of sub-pixels and formed by sequentially filling the view image kj′,4m+k at a position i according to the rule of i=4 m+k (m is a positive integer including 0 and k=0˜3). Further, on any vertical line (e.g., i=i′, where i′=4m×k, m is a positive integer including 0 and k=0˜3), the 4-view image arrangement Vj,i is in unit of sub-pixels and formed by sequentially filling the view image kj,i′ on a column i′ of the same k-view image at a position j.
Due to characteristics of the optical structure of the vertical strip parallax barrier 10, the vertical strip light-transmissive elements 11 and the vertical strip shielding elements 12 in the structure realize the effect of separating the multi-view 3D image only in the horizontal direction through the light transmission and shielding function. Therefore, it only needs to study a single horizontal structure for analyzing the optical characteristics.
FIG. 3 is a schematic view of the display principle of a conventional 4-view parallax barrier 3D image display.
The 4-view image Vi,j is in unit of sub-pixels and arranged on a display screen 100 (for ease of illustration, only a part of the image on the horizontal line is shown and V0, V1, V2, V3 are used to replace Vi,j). Through the function of the 4-view parallax barrier 110, the 4-view images V0, V1, V2, V3 can be observed at four best viewing points P0, P1, P2, P3 (let LV be the distance between the best viewing points) on an optimum viewing distance Z0. Therefore, as long as eyes 120, 121 (with an eye interval of LE) of a viewer are located at any two neighboring best viewing points (in a relation of LE=LV), the viewer may observe a perfect 3D image. The coverage of the four best viewing points P0, P1, P2, P3 forms a viewing zone. Hence, the function of the parallax barrier is to completely separate the view of the multi-view 3D image at the four best viewing points P0, P1, P2, P3 on the optimum viewing distance. Additionally, the distance LV of the best viewing points is defined by the following formula:
                              L          V                =                              P                          P              -                              B                0                                              ⁢                      B            0                                              (        1        )            
where B0 is a width of the light-transmissive elements and P is a width of a sub-pixel.
The optimum viewing distance Z0 (the distance to the display screen 100) is defined by the following formula:
                              Z          0                =                              P                          P              -                              B                0                                              ⁢                      L            B                                              (        2        )            
where LB is the installation distance for the parallax barrier 110 (the distance to the display screen 100).
The theory for deducing Formulae (1) and (2) may refer to the following paper:
“Theory of Parallax Barriers”, Sam H. Kaplan, Vol. 59, Journal of the SMPTE, 1952.
The paper issued by Kaplan in 1952 discloses the calculation of Formulae (1) and (2), but does not discuss the ghost image phenomenon and the optimum design of the parallax barrier. So far, although ROC Patent No. 097135421 discusses the ghost image phenomenon and proposes a method to solve the problem, but does not provide any solution for the ghost image phenomenon generated by different eye interval and viewing positions. Hereinafter, the causes of the two phenomena are first explained and a solution is provided.
FIG. 4 shows a viewable range LS of the views V0, V1, V2, V3 on the optimum viewing distance. The generation of the viewable range is described in ROC Patent No. 097135421. On the optimum viewing distance Z0, the viewable range of a single view V0˜V3 is in a relation of LS=2LV. Thus, the viewable range of a single view V0˜V3 is overlapped with the viewable ranges of two neighboring views, which is a root cause of the ghost image. That is to say, in a horizontal direction, when the eye interval of the viewer is different from the distance LV of the best viewing points, or the viewing positions of the two eyes are not located at the best viewing points, the ghost images are generated. Hereinafter, such ghost image is referred to as a transverse ghost image.
FIG. 5 shows a ghost image phenomenon generated when the eye interval LE≠LV. Provided that the left eye 120 is located at the best viewing point P2, since the eye interval LE≠LV, the right eye 121 is deviated from the best viewing point P1. Thus, the right eye 121 may observe the views V1 and V2 (when LE<LV) at the same time or observe the views V1 and V0 (when LE>LV, not shown) at the same time.
FIG. 6 shows a ghost image phenomenon generated by the wrong viewing position. Even if the eye interval LE=LV, due to the wrong viewing position, the left eye 120 observes the views V1 and V2 at the same time, and the right eye 121 observes the views V0 and V1 at the same time.